Mohan

Several of my partners (including Ed Davis) prefer
John Mohan's defense against weak notrumps. We define
"strong" to be "any 1NT opening that includes 16 HCP, but
in addition 13-15 HCP played in conjunction with a
big club system." All weaker than that are "weak."

The basic idea is to use transfers in order to give
the overcaller a chance to bid twice with very good
hands. Initial actions are:

Dbl

Good 14+, usually balanced

2

Both majors

2

Transfer to hearts

2

Transfer to spades

2

Spades and a minor

2NT

Hearts and a minor

3

Natural

3

Natural

3

Natural, preemptive

3

Natural, preemptive

Note that initial actions are sound overcalls. Most overcalls
are something that resembles a decent opening bid with some
playing strength. This means that we might get shut out with
13 vs. 13, but since it is quite possible that we have
a game, we can't afford to bid light and get doubled at the
3-level after a game try.

Advancer's Actions

After an initial double, some play system on, some
play natural. In either case, I suggest making a
2 response to the double be a scramble, not
showing much of anything, just usually fear. It might
be a reasonable shapely hand that doesn't want to play
1NT doubled and doesn't have a convenient way out, but
that's rare. A redouble of 2 is takeout.
We play system on if their pass is forcing to a redouble,
but system off otherwise.

If they redouble for business, pass is to play. System
should definitely be off.

We play that after a double, the next double is takeout,
usually showing exactly two cards in their suit. Others
prefer that the first double is only semi-natural and
just shows extra values. Discuss this with partner.

We play that after 1NT is doubled, we are in a force
through 2. Some prefer to make this 2,
because the force on 2 usually leads to our
contract of 2, whereas being forced vs.
2 forces us to the three-level.

In response to 2, 2 shows no or little
preference. This is quite helpful if overcaller is 5-4.
2NT is a natural game try. Jumps are invitational.
3 is to play. 2 followed by 3
is forcing.

In response to the transfers, all bad hands simply accept
the transfer. New suits are natural and forward-going,
but not 100% forcing. 2NT is a natural game try. Jump
acceptances are invitational. Yes, there is no force.
That probably ought to get changed.

In response to 2 showing spades and a minor,
2NT is an artificial game try, asking for size and
the minor. 3 is pass or correct. 3 is
invitational.

Over 2NT, showing hearts and a minor, 3 is
pass or correct, 3 is natural and forward-going,
3
is to play, and 3 is natural and forcing.

Overcaller's Rebids

Everything is pretty much natural; second bids show
extra strength. One strangeness is that a transfer
to a major followed by a minor shows a four-card major
and a six-card minor.